Agriculture includes both subsistence agriculture, which is producing enough food to meet the needs of the farmer and family (but no more), and also (almost universally in the "developed" nations and increasingly so in other areas) the production of financial income from cultivation of the land or commercial raising of animals (animal husbandry). Agriculture is the practice -- the study of these disciplines is called agricultural science.

In the Western world, use of improved genetics, better management of soil nutrients, and improved weed control have greatly increased yields per unit area. At the same time, use of mechanization has decreased labor requirements, releasing most of the populace from intense agricultural labor. The developing world is behind by Western measures of productivity, because of unavailability of the education, capital and technology base needed to sustain these advances, and usually ecoregion with less optimal climates and soils.

Modern agriculture depends heavily on engineering and technology and on the biological and physical sciences. Irrigation, drainage, conservation, and sanitary engineering—each of which is important in successful farming—are some of the fields requiring the specialized knowledge of agricultural engineers.

Agricultural chemistry deals with other vital farming concerns, such as the application of fertilizer, insecticides (see Pest control), and fungicides, soil makeup, analysis of agricultural products, and nutritional needs of farm animals.

Plant breeding and genetics contribute immeasurably to farm productivity. Genetics has also made a science of livestock breeding. Hydroponics, a method of soilless gardening in which plants are grown in chemical nutrient solutions, may help meet the need for greater food production as the world’s population increases.

The packing, processing, and marketing of agricultural products are closely related activities also influenced by science. Methods of quick-freezing and dehydration have increased the markets for farm products (see Food Processing and Preservation; Meat Packing Industry).

Mechanization, the outstanding characteristic of late 19th- and 20th-century agriculture, has eased much of the backbreaking toil of the farmer. More significantly, mechanization has enormously increased farm efficiency and productivity (see Agricultural Machinery). Animals including horses, oxen, llamas, alpacas, and dogs, however, are still used to cultivate fields, harvest crops, and transport farm products to markets in many parts of the world.

Airplanes and helicopters are used in agriculture for seeding, spraying operations for insect and disease control, transporting perishable products, and fighting forest fires. Radio and television disseminate vital weather reports and other information such as market reports that concern farmers. Computers have become an essential tool for farm management.

Animal husbandry means breeding and raising animals for meat or to harvest animal products (like milk, eggs, or wool) on a continual basis.

In recent years, some aspects of industrial intensive agriculture have been the subject of increasing discussion. The widening sphere of influence held by large seed and chemical companies and meat packers has been a source of concern both within the farming community and for the general public. The patent protection given to companies that develop new types of seed using genetic engineering has allowed seed to be licensed to farmers in much the same way that computer software is licensed to users. This has changed the balance of power in favor of the seed companies, allowing them to dictate terms and conditions previously unheard of. Some argue these companies are guilty of biopiracy.

Soilconservation and nutrient management have been important concerns since the 1950s, with the best farmers taking a stewardship role with the land they operate.

Nangtukeun asal-usul tatanén bisa disebut hésé sabab geus aya méméh budaya tulisan. Sababaraha ahli keukeuh nyebutkeun yén tatanén geus aya leuwih ti 10000 taun katukang, sedengkeun nu séjén yakin yén pepelakan nu sistimatis pangheubeulna teu leuwih ti 7000 taun katukang. Prakprakan tatanén mindeng dipaké pikeun ngabédakeun jaman néolitik ti jaman batu nu saméméhna. Palawija nu munggaran dibudidayakeun ku manusa di antarana gandum (einkorn jeung emmer) sarta barley. It is clear that farming was invented at least twice, probably more often: once in the Fertile Crescent during the Natufian culture, and the following Pre-Pottery Neolithic A and B periods, once in East Asia (wheat and millet), and in Central America (maize). Most likely, there was a gradual transition from a hunter-gatherer economy to an agricultural one, via a lengthy period when some crops were deliberately planted, and other foods were gathered from the wild. The reasons for the earliest introduction of farming may have included climate change. Farming allows a much greater density of population than can be supported by hunting and gathering.

After 1492, the world's agricultural patterns were shuffled in the widespread exchange of plants and animals known as the Columbian Exchange. Crops and animals that were previously only known in the Old World were now transplanted in the New, and vice versa.

Domestication of plants is done in order to increase yield, disease resistance, drought tolerance, ease of harvest, and to improve the taste and nutritional value and many other characteristics. Centuries of careful selection and breeding have had enormous effects on the characteristics of crop plants. Plant breeders use greenhouses and other techniques to get as many as three generations of plants per year, so that they can make improvements all the more quickly. Extensive radiation mutagenesis efforts (i.e. primitive genetic engineering) during the 1950s produced the modern commercial varieties of grains such as wheat, corn and barley.

For example, average yields of corn (maize) in the USA have increased from around 2.5 tons per hectare (40 bushels per acre) in 1900 to about 9.4 t/ha (150 bushels per acre) in 2001, primarily due to improvements in genetics. Similarly, worldwide average wheat yields have increased from less than 1 t/ha in 1900 to more than 2.5 t/ha in 1990. South American average wheat yields are around 2 t/ha, Afrika under 1 t/ha, Mesir and Arabia up to 3.5 to 4 t/ha with irrigation. In contrast, the average wheat yield in countries such as Perancis is over 8 t/ha. Higher yields are due to improvements in genetics, as well as use of intensive farming techniques (use of fertilizers, chemical pest control, growth control to avoid lodging).

Very recently, genetic engineering has begun to be employed in some parts of the world to speed up the selection and breeding process. The most widely used modification is a herbicide resistance gene that allows plants to tolerate exposure to glyphosate. A less frequently used but more controversial modification causes the plant to produce a toxin to reduce damage from insects (c.f. Starlink).

There are specialty producers who raise less common types of livestock or plants.